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Rickettsia Flashcards

1
Q

What causes rickettsia

A

Rickettsiaceae

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2
Q

What do rickettsia genus cause

A

Spotted fever
Typhus fever
Scrub typus

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3
Q

Causes of spotted fever

A

Rickettsia rickettsii (rocky mountain) - orth america
Rickettsia akrai (boutonneuse fever)
Rickettsia sibricia , australis felis - flea, japnoica, africae
African tick bite fever

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4
Q

Typhus group of rickettsiae causative organsims

A

Rickettsia prowazekii - epidemic typhus, recrudescent typhus, sporadic typhus
Rickettsia typhi - murine typhus (endemic typhus)

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5
Q

Scrub typhus group causative organisms

A

Rickettsia tsutsuganmushi

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6
Q

What is scrub typhus

A

Acute febrile infectious disease caused by orientia tsutsugamushi

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7
Q

Symptoms of rickettsia

A

Eschar
Regional lymphadenopathy
Fever
Maculopapular rash
Leukopenia

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8
Q

What is o.tsutsugamushi sensitive to

A

Chloramphenicol and tetracycline

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9
Q

Source of infection and transmission of rickettsia

A

Rat -> trombiculid mites
Transmitted to humans by arthropods - ticks, mice, louse, flease
Larva of trombiculid mite
Spread by haematogenous or lymphatics

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10
Q

Immunity to serotypes once have rickettsia

A

Only to that serotype - no protection from others

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11
Q

What is the tsutsugamushi traingale

A

Geographical area where ecposed to rickettsia -
Northern japan and far eastern russia
to northern australia to pakistan and afghanistan
Jungle, scrub and grassland

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12
Q

Seasonal peaks in north vs sotuh

A

South - may to cotober with maximal peak june to july
North - septmeber to december w maximal peak in october

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13
Q

Features of o.tsutsugamushi bacteria

A

Obligate intracellular parasites
Gram negative coccobacilli
RNA and DNA (binary fission_
Stains red on giemsa or gimenez stain

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14
Q

What colour does o.tsutsugamushi stain on giemsa or gimenez stian

A

Red

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15
Q

Pathogenesis of rickettsia

A

Maculopapular rash, eschar, ulcer
Enlargement of local ly,ph node -> blood
General symptoms sepsis -> generalised hyperaemia, systemic lymphadenopath

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16
Q

INcubation period of rickettsia

17
Q

Presentation of firs week of ricketttsia

A

Sudden onset of fecer - systemic toxic symptoms

18
Q

2nd week vs 3rd week of rickettsia

A

3rd week - Worse, complications, 4th week convalesce

19
Q

What is eschar

A

Ulcer surrounded by red arcola often overed by dark scab

20
Q

Most common areas for eschar location

A

Axillary fossa, inguinal region, perianal region, scortum, buttocks, thigh

21
Q

What is most specific manifestation of scrub typhus

22
Q

Specific features of rickettsia

A

Eschar
Maculopapular rases (end of first week, chest, abdo, trunk, upper or lower limbs)
Local lymphadenopathy

23
Q

Haematology/biochemical markers of rickettsia

A

Leukopenia
Normal WCC
Elevated w complications
Injury of liver function, CRP

24
Q

What test for rickettsia

A

weil-felix test (esp in healthcare restricted settings)

25
How early can weil felix be psotivie
4th day after onset
26
What is diagnostic from weil-felix test
>1:160 or increase 4 fold during course Poor specialisation
27
What is gold standard tests for rickettsia
Indirect fluroescent antibody - IFA - IIP - indirect immunosperoxidase test
28
When can IFA for rickettsia be postive from
positive from end of first week Lasts for years
29
Pathogenic examination for rickettsia
Culture - use in mouse Spleen and liver biopsy - stain with giemsa PCR - orientia DNA Not routinely available
30
Early course pathology of rickettsia
Perivascular lymphohistiocytic infiltrate and extravasated erythrocytes and dermal oedema Dermal and epidermal necoriss later positive r.rickettsiae imunohistochemical stain
31
Criteria for diagnosis of rickettsia
Visit endemic area last 3 weeks - work ,camp, grass sit Clinical manifestation Lab exam - weil feliz reaction
32
Differential diangoses rickettsia
Epidemic typhus - winter and spring louse bite, weil-felix and OX19 + Typhus Leptospirosis Dengue Kawasaki Malaria MEasles Meningococcal Rubella Strep A Syphilis Toxic shock syndrome Vasculitis, thrombophlebitis
33
Typhus features
slow onset fever. Confusion, bradycardia, digestive symtpoms, rose rash, no eschar, widal test positive + culutre of typhus bacilus positive
34
Leptospirosis how differntiate
Calf muscle tenderness Microscopic haematuria
35
General treatment
IV fluids supportive Intensive nursing care and prevent complication Sensitive antibitics - mortality drastically reduced
36
Treatment regimes for rickettsia
Chloramphenicol - 2g/day (25mg/kg child) Doxycycline - 0.2g/day adult (tetracycline alt) Azithromycin 500mg daily Roxithromycin - 0.6g/day adult - 2-3mg/kg/day child ESP in child useful
37
Treatment if resistnat rickettsia strain
Combination therapy doxycycline and rifampacin Azithromycin

Infectious disease (37 decks)

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